The objective of this project is to determine the effect that the neuropeptide fragment ACTH 4-10 has upon the cognitive abilities of young and elderly individuals. This drug has been suggested to facilitate the efficiency of a number of mental operations including arousal, selective attention, and memory retrieval. We will use the conceptual and methodological paradigms on the information processing model of experimental psychology to test for changes in these cognitive functions in subjects taking a synthetic form of ACTH 4-10. Every subject will take part in five testing sessions, each with a different dosage level of the drug. A double blind, complete crossover design will be used. The age of the subjects will be an important variable in as much as elderly individuals have been shown to have some problems in all of the cognitive functions to be tested, and thus will be more likely to show a substantial drug effect. Most of the tasks used will measure the effect of the drug on the speed with which the subject can carry out a given mental operation. We will examine the effect of ACTH 4-10 on subjects' ability to: 1) use prior information to selectively attend to only the relevant cues in a visual search task; 2) use a warning cue to speed up their response in a disjunctive reaction time task; 3) retrieve information from long-term memory rapidly. In addition, we will examine whether the drug primarily affects subjects' ability to perceive a stimulus (sensitivity) or instead, whether it alters the criterion they use to make their decision. From these studies we hope to learn whether ACTH 4-10 affects certain specific mental operations, and whether this affect is greater in the elderly. If this drug does enhance cognitive performance in the elderly, it may be useful in treating some of the cognitive deficits which are often associated with advanced age. Similar studies will also be conducted using a related neuropeptide (vasopressin) also thought to affect cognitive performance.